anderson@mrcnext.uiuc.edu (Brent James Anderson) (02/17/91)
Friend says that there really isn't such a thing as "32-bit" memory. Everyone always says, "you have to get some 32bit mem. if you're going to buy an '030 board or else it'll crawl... etc." but he says that the only difference is the size (ie: 1x8, 256x4...) and the refresh speed (ie: 80ns, 100ns...). I really have no solid argument bec. I just don't know enough. But everyone says that I have 16bit memory on my standard Amiga 2000 and I must get 32bit ram for any '030 board I buy. Please help, I wouldn't mind if actually is right. -Beej
ig29@terre (Robert Gagnon) (02/17/91)
In article <anderson.666764399@mrcnext> anderson@mrcnext.cso.uiuc.edu writes: >Friend says that there really isn't such a thing as "32-bit" memory. > >Everyone always says, "you have to get some 32bit mem. if you're going >to buy an '030 board or else it'll crawl... etc." > >but he says that the only difference is the size (ie: 1x8, 256x4...) >and the refresh speed (ie: 80ns, 100ns...). > Your friend is right. Everyone also is. Have I got you confused now? ;) When somebody refers to 32-bit memory, he is talking about the way the memory is accessed. To access memory 32 bit at a time, you could use 32 1meg x 1bit chips, or 8 256K x 4 bit chips. The chips don't matter, it is the width of the bus to access them that is important. If you have a Zorro II memory card, it can only be accessed 16 bits at a time (because Zorro II is a 16 bit bus). So your card would be referred to as a 16 bit memory card. If you have a 32 bit processor, you really want to have 32 bit memory (that is, memory that is accessed via a 32 bit bus) to let the processor run at full speed. Hope I helped. Robert // \X/ Gagnon
dave@cs.arizona.edu (Dave P. Schaumann) (02/17/91)
In article <anderson.666764399@mrcnext> anderson@mrcnext.cso.uiuc.edu writes: >Friend says that there really isn't such a thing as "32-bit" memory. Dang. The jig is up. Hey, everybody, no more raking in big bucks on the "32-bit" scam. >[...] >but he says that the only difference is the size (ie: 1x8, 256x4...) >and the refresh speed (ie: 80ns, 100ns...). Ok. Here's a basic hardware lecture. You got your CPU, and you got your memory. They communicate through a "bus", which is really just some wires. The size of this bus determines how much data can be read and written to memory in one operation. On the 6502, the bus could transfer 8 bits at a time. That is why the 6502 is called an 8-bit CPU (even though addresses are 16 bits). Now, the 68000 is a 16-bit CPU (ie, 16-bit communication between the CPU and memory). This means, for example, if you want to load a long word from memory into the CPU, it takes 2 memory fetches, even though it is one machine op. Now this memory-CPU bus is sometimes called the Von Neuman (sp?) bottleneck, since memory response time is typically ~10 times slower than the CPU clock speed. This means that every time you want to read memory, the CPU has to wait for about 10 clock cycles. Perhaps now you begin to see the advantage of a 32-bit bus. A longword load will now go nearly twice as fast. A smart CPU will also be able to take advantage of this for byte and word accesses too, since memory is typically accessed in a sequential manner. I'm not familiar with the hardware architecture of the 680x0 family, so I can't really be more specific about Amiga hardware than that. But that's the jist of Why 32 Bit Memory Is A Good Thing. >Please help, I wouldn't mind if actually is right. Sorry. No such luck. -- Dave Schaumann | DANGER: Access holes may tear easily. Use of the access | holes for lifting or carrying may result in damage to the dave@cs.arizona.edu | carton and subsequent injury to the user.
tinyguy@cs.mcgill.ca (Yeo-Hoon BAE) (02/17/91)
In article <1991Feb17.050114.9629@DMI.USherb.CA> ig29@terre (Robert Gagnon) writes: >In article <anderson.666764399@mrcnext> anderson@mrcnext.cso.uiuc.edu writes: >>Friend says that there really isn't such a thing as "32-bit" memory. >> >If you have a 32 bit processor, you really want to have 32 bit memory (that is, >memory that is accessed via a 32 bit bus) to let the processor run at full >speed. > So for example, can you use a normal 1x8 SIMMS modules of 80ns, to be accessed by a 32bit processor? Or does it need other SIMMS ? -TG
ig29@terre (Robert Gagnon) (02/18/91)
In article <1991Feb17.070347.15673@cs.mcgill.ca> tinyguy@cs.mcgill.ca (Yeo-Hoon BAE) writes: >In article <1991Feb17.050114.9629@DMI.USherb.CA> ig29@terre (Robert Gagnon) writes: >>In article <anderson.666764399@mrcnext> anderson@mrcnext.cso.uiuc.edu writes: >>>Friend says that there really isn't such a thing as "32-bit" memory. >>> >>If you have a 32 bit processor, you really want to have 32 bit memory (that is, >>memory that is accessed via a 32 bit bus) to let the processor run at full >>speed. >> > >So for example, can you use a normal 1x8 SIMMS modules of 80ns, to be accessed >by a 32bit processor? Or does it need other SIMMS ? > 1meg by 8 SIMMS could be used with a 32 bit processor (and bus). In fact, I think they ARE used with the GVP accelerators. Robert // \X/ Gagnon
lkoop@pnet01.cts.com (Lamonte Koop) (02/18/91)
tbissett@nstar.rn.com (Travis Bissett) writes: >anderson@mrcnext.uiuc.edu (Brent James Anderson) writes: > >> Friend says that there really isn't such a thing as "32-bit" memory. >> >> Everyone always says, "you have to get some 32bit mem. if you're going >> to buy an '030 board or else it'll crawl... etc." >> >> but he says that the only difference is the size (ie: 1x8, 256x4...) >> and the refresh speed (ie: 80ns, 100ns...). >> > >I'm afraid your friend is a bit confused <roar! pun intended :-)> The chips No, his friend is correct. >that constitute the 32-bit memory may or may not be of particular interest. >There are two big things to be considered as part of 32-bit ramhood: (1) the >memory chips have to have address lines that correspond to the 32 signal >lines coming form the 680x0 cpu; (2) the data buss has to have the bandwidth The pin makeup of the chips is of interest for external circuitry design considerations, and has nothing to do with whether or not the chips may be used as "32-bit memory". Basically, the chips are not important in this issue, but what is important is the complete board/device design. A memory board designed to be used on a 32-bit wide bus will have it's controlling circuitry also designed for utilizing the chips it has in a 32-bit data transfer manner. This may involve interleave setups, and so on, depending on the size and density of the memory, but does not depend on the acutal chip in that the memory chips themselves do not have to be "32-bit" chips. Yes, data transfers can occur for amounts less than a full 32-bits at a time, as the bus bandwidth is the upper limit to the simultaneous transfer size. >Travis Bissett NSTAR conferencing site 219-289-0287 >internet: tbissett@nstar.rn.com 1300 newsgroups - 8 inbound lines >uucp: ..!uunet!nstar.rn.com!tbissett 99 file areas - 4300 megabytes >--- backbone news & mail feeds available - contact larry@nstar.rn.com --- LaMonte Koop Internet: lkoop@pnet01.cts.com ARPA: crash!pnet01!lkoop@nosc.mil UUCP: {hplabs!hp-sdd ucsd nosc}!crash!pnet01!lkoop "Yes, I am their leader...now tell me where they went!"
peterk@cbmger.UUCP (Peter Kittel GERMANY) (02/18/91)
In article <anderson.666764399@mrcnext> anderson@mrcnext.cso.uiuc.edu writes: >Friend says that there really isn't such a thing as "32-bit" memory. > >Everyone always says, "you have to get some 32bit mem. if you're going >to buy an '030 board or else it'll crawl... etc." > >but he says that the only difference is the size (ie: 1x8, 256x4...) >and the refresh speed (ie: 80ns, 100ns...). Your friend talks about a single RAM chip. And they indeed come at 8 bits maximum "data bus width". But when speaking of 32 bit, we normally mean the whole RAM system, made of several (many) RAM chips. And this can indeed be configured with 32 bit width. >I really have no solid argument bec. I just don't know enough. But >everyone says that I have 16bit memory on my standard Amiga 2000 >and I must get 32bit ram for any '030 board I buy. You need the respective processor that can handle the databus width. In an A2000, you only can use 16-bit RAM, but if it is upgraded with an 020 or 030, 32-bit memory really makes sense. -- Best regards, Dr. Peter Kittel // E-Mail to \\ Only my personal opinions... Commodore Frankfurt, Germany \X/ {uunet|pyramid|rutgers}!cbmvax!cbmger!peterk
daveh@cbmvax.commodore.com (Dave Haynie) (02/19/91)
In article <anderson.666764399@mrcnext> anderson@mrcnext.cso.uiuc.edu writes: >Friend says that there really isn't such a thing as "32-bit" memory. "Friend" needs some memory lessons. >Everyone always says, "you have to get some 32bit mem. if you're going >to buy an '030 board or else it'll crawl... etc." That's true. What "32 bit memory" refers to is the width of the data bus going to the memory system. The 68030 can transact with 8, 16, or 32 bit memory systems. But, all things being equal, it must hit an 8 bit memory system 4 times as much as a 32 bit system to do the same work. So, for the same speed memory system, a 32 bit memory system is roughly twice as fast as a 16 bit memory system. On Amigas, there's more difference than that, however. No one makes fast 68030 bus style 16 bit memory boards. All the 16 bit memory boards are Zorro II bus boards or "sits on the 68000 socket" hacks. In either case, these are 16 bit memory board designed for a 7MHz 68000. The 32 bit memory systems are all faster, in addition to being wider. >but he says that the only difference is the size (ie: 1x8, 256x4...) >and the refresh speed (ie: 80ns, 100ns...). No. Memory _chips_ themselves come in different packages. These packages are generally either 1 or 4 bits wide, though some new DRAMs come as wide as 16 bits. You shouldn't be too concerned with the width of the chip. I can build a 32 bit wide memory system from thirty-two 1-bit-wide DRAMs, eight 4-bit-wide DRAMs, or for that matter, two 16-bit-wide DRAMs. The speed rating, 80ns, 100ns, etc. is the access time, not the refresh time. Access time is a general indicator of how fast that part can be run. The memory board design, not the memory chip itself, determines how fast the memory actually is run. >-Beej -- Dave Haynie Commodore-Amiga (Amiga 3000) "The Crew That Never Rests" {uunet|pyramid|rutgers}!cbmvax!daveh PLINK: hazy BIX: hazy "What works for me might work for you" -Jimmy Buffett
daveh@cbmvax.commodore.com (Dave Haynie) (02/19/91)
In article <887@caslon.cs.arizona.edu> dave@cs.arizona.edu (Dave P. Schaumann) writes: >Now this memory-CPU bus is sometimes called the Von Neuman (sp?) bottleneck, >since memory response time is typically ~10 times slower than the CPU clock >speed. This means that every time you want to read memory, the CPU has to >wait for about 10 clock cycles. >[...] >I'm not familiar with the hardware architecture of the 680x0 family, so I >can't really be more specific about Amiga hardware than that. I'm sure alot of other aren't either. It can be confusing. Perhaps the most confusing thing around is the clock speed vs. bus speed question. The 68000, for instance, has a 7.09MHz or 7.16MHz clock in Amiga systems. It takes the 68000 a minimum of 4 clock cycles to run a complete memory cycle. At 7.16MHz, this means that a minimal memory cycle is about 560ns long. We have had memory fast enough to cycle in that period for year. In fact, Chip RAM actually runs a 280ns cycle, one cycle for the CPU, one for display, when you have your normal Workbench screen up. Nearly all add-on memory boards for these systems run at the full speed. Now look at a typical 68030 based Amiga, like the A2630 or A3000. The 68030 gets a 25MHz clock, and takes only 2 clock cycles to run a complete memory cycle. This results in an 80ns cycle time. Even the fastest dynamic memories around can't get close to that (the _cycle_ time on a part is roughly twice the indicated access time, so typical 80ns DRAMs need 160ns to cycle fully). The typical 25MHz 68030 memory cycles in 200ns, or 5 clocks. That's enough to work with 100ns DRAM, if you have a very fast memory controller, or 80ns DRAM with a moderately fast DRAM controller. Motorola knew when they designed the '030 that it would have a hard time finding fast enough memory, so they added this "burst mode" that you often hear about. This is a specialized mode that matches closely to specialized DRAM modes to let 3 additional words be accessed fast once one is accessed at normal speed. The 68030 can read one of these extra words per clock. In the A3000, the memory system can provide such burst reads in two clocks per word. So, instead of reading 4 consecutive longwords in 20 clocks, the A3000 can do it in 11 clocks if there's static column memory in it. That averages to 2.75 clocks per word, close to the ideal time of 2 clocks per word. >Dave Schaumann | DANGER: Access holes may tear easily. Use of the access -- Dave Haynie Commodore-Amiga (Amiga 3000) "The Crew That Never Rests" {uunet|pyramid|rutgers}!cbmvax!daveh PLINK: hazy BIX: hazy "What works for me might work for you" -Jimmy Buffett
bryanh@amix.commodore.com (Bryan Harpel) (02/19/91)
> the special chips, but you Really Want 32-bit for other ram if you have > higher than 68000 cpu. There is an important difference here. > I am about to buy 32 bit ram for my GVP Accel. board. I was curious about 1 thing, I can only afford to get the 2 meg version as of now. Will it run slower than if I got the 4 meg version, or is two megs of 32 bit enough to help out the 68030's BURST mode? In case you are wondering, I play alot of flight simulators and the such, but no raytracing or anything (very rarely). Thanx in advance. /// Only - Bryan /// AMIGA \\\/// Makes it \XX/ Possible.... ----------------------------------------------------------------------------- Bryan Harpel UUCP: {rugters|uuwest|uunet}!cbmvax!amix!undrground!bryanh INTERNET: undrground!bryanh@amix.commodore.com "You will die by my hand, For it is I who rule the land"
daveh@cbmvax.commodore.com (Dave Haynie) (02/19/91)
In article <yBqLX1w163w@undrground> undrground!bryanh@amix.commodore.com (Bryan Harpel) writes: >> the special chips, but you Really Want 32-bit for other ram if you have >> higher than 68000 cpu. There is an important difference here. > I am about to buy 32 bit ram for my GVP Accel. board. I was curious >about 1 thing, I can only afford to get the 2 meg version as of now. >Will it run slower than if I got the 4 meg version, or is two megs of 32 >bit enough to help out the 68030's BURST mode? That depends completely on the GVP's design. Some designs require 4 MB chunks to support burst mode, others work in smaller chunks, like the A3000's memory system. This depends on the kind of memories, the size of memories, etc. Unless anyone around here specifically knows the GVP memory board's specifics, your best bet would be to call GVP. Using memory chips, it works out something like this. There are three kinds of "special" memory modes which can be used to support burst mode: page mode, static column mode, and nybble mode DRAMs. Nybble mode looks just like the 68030 burst mode, so it hooks up with practically no extra "magic". However, at least when I was working on the A2630, you could only get nybble mode parts in 1 bit packages. So, for a 32 bit bus, the minimum "bank" of memory would come out at 4MB, but we had to support 2MB. So no burst. On the A3000, we use static column memories to run burst mode. Static column and page mode memories are very similar in many respects, especially in the fact that they don't naturally support burst mode. So you need additional, fast logic to get them to coexist with burst mode. The high integration of the A3000's memory controller made this a reasonable thing to do. >Bryan Harpel -- Dave Haynie Commodore-Amiga (Amiga 3000) "The Crew That Never Rests" {uunet|pyramid|rutgers}!cbmvax!daveh PLINK: hazy BIX: hazy "What works for me might work for you" -Jimmy Buffett